PCMCIA modems and PCMCIA fax modems enable computers to transmit data over telephone lines. Because computer data is digital and information sent over phone lines is transmitted in analog waves, a modem (modulator-demodulator) is needed to convert between these forms. Fax modems are similar to data modems, but are designed to transmit and receive documents to and from a fax machine, or another fax modem. Both PCMCIA modems and PCMCIA fax modems take their name from the Personal Computer Memory Card Association (PCMCIA), the organization that develops and maintains standards for PCMCIA cards. Originally known as PC cards and used to add memory to portable computers, PCMCIA cards are now used in many applications.
There are three basic types of PCMCIA modems and PCMCIA fax modems: modem-only devices, modem and fax combinations, and fax/modem products with networking capabilities. As with other types of PCMCIA cards, PCMCIA modems and PCMCIA fax modems are available with several different form factors. Type I cards are 54 mm x 85.4 mm, and can be up to 3.3 mm thick. Type II cards are 54 mm x 85.4 mm, and can be up to 5.5 mm thick. Type III cards are 54 mm x 85.4 mm, and can be up to 10.5 mm thick. Type IV cards have not yet been ratified by the PCMCIA consortium; however, their size is expected to be 54 mm x 85.4 mm with a thickness of 18 mm. Additional form factors for PCMCIA modems and PCMCIA fax modems include SmartMedia Card, CompactFlash, Miniature Card, Solid State Floppy Disk (SSFDC), and MultiMediaCard (MMC).
PCMCIA modems and PCMCIA fax modems differ in terms of modem technology, fax mode, maximum modem speed, and maximum fax speed. Choices for modem technology include K56Flex, V.90, V.34, and V.34+. Choices for fax mode include V.17, V.29, V.27ter, and V.21 Channel 2. With the exception of K56Flex, all of these standards are defined by International Telecommunications Union (ITU-T). Maximum modem speed and maximum fax speed are additional specifications to consider when selecting PCMCIA modems and PCMCIA fax modems. For maximum modem speed, the choices are 9.6, 14.4, 28.8, 33.6, and 56 kbps. For maximum fax speed, the choices are 7.2, 9.6, and 14.4 kbps.
Product specifications for PCMCIA modems and PCMCIA fax modems include technology standards and operating modes. The most common technology standards are PC Card Standard 95, CardBus, StrataFlash ® (Numonyx B.V.), and CompactFlash ® (CompactFlash Association). Operating modes include full duplex, half duplex, tone and pulse dial, and voice/audio mode. Full duplex PCMCIA modems can transmit data in both directions at the same time. Half duplex modems can transmit data in just one direction at a time. Tone and pulse dial fax/modems can communicate using a dial pulse or dial tone. PCMCIA modems and PCMCIA fax modems with voice/audio mode can be used in either data mode or voice (audio) mode.